An experimental investigation for flexural strengthening of RC beam using externally unbonded mild steel flat bar

This study was devoted towards an experimental investigation to evaluate the effectiveness of a newly proposed strengthening technique for flexure deficient RC beam. In the proposed technique, the beam was strengthened using readily available mild steel (MS) flat bar and royal bolt to make the process quick and economic. The effects of various important factors viz., the number of bolt and its diameter, thickness and size of flat bar and their location were investigated using four-point bending test. Test results revealed that the proposed strengthening technique is effective enough to enhance the load carrying capacity of the control beam in flexure. The yield and ultimate strengths increased by as much as 45% compared to the control beam in one of the strengthened cases. It was found that the size and thickness of MS flat bar and its location have noticeable influence on the flexure capacity of the strengthened beam. The anchorage failure of royal bolt was the dominant mode of failure, and the effectiveness of the method mainly depends on the performance of the royal bolt anchorage. The royal bolt failure could be avoided by providing enough number of royal bolts to utilize the full tensile capacity of the MS flat bar and improve the flexure behavior of the strengthened beam.